In a liquid manure storage system, the manure is initially delivered to a pit in the barn or other livestock area. The manure is then diluted with water and homogenized in the pit, and then pumped through an underground line to a large open top manure storage tank. The liquid manure is stored for long periods of several months or more in the storage tank, and during storage the lighter-than-liquid fibrous material, such as straw and hay derived from animal bedding, will stratify as an upper layer above the liquid and heavier-than-liquid solids. Over a period of time, the lighter, fibrous materials, form a thick crust on the top of the tank and depending upon the amount of fibrous material and the time of accumulation, the crust can be several feet thick.
When it is desired to withdraw the liquid manure from the storage tank, it is necessary to break up the crust and homogenize the mass, so that it can be pumped into a mobile tank for spreading on the fields.
U.S. Pat. No. 4,332,484 describes an agitation system for a liquid manure tank which is utilized to agitate and homogenize the liquid slurry, so that it can be pumped from the tank. In accordance with the agitation system of the aforementioned patent, the liquid manure is withdrawn from the bottom of the tank through a supply line by a pump which is located on the exterior of the tank. The discharge of the pump, through valving, can either deliver the liquid manure through a conduit embedded in the tank foundation to a center rotatable agitator, or alternately, deliver the liquid manure to a vertical delivery pipe which extends upwardly along the wall of the tank where the slurry can then be discharged through a nozzle into the open end of the tank to break up the crust. As a third route of delivery, the liquid manure, after homogenizing, can be delivered by the pump to a discharge pipe for discharge to a mobile manure spreader.
In order to properly break up the thick crust on the top of the tank, it is necessary to periodically change the direction of discharge of the over-the-top nozzle. For example, in breaking up the crust, it may be necessary to direct the liquid manure to a given area in the crust for several hours to develop a hole in the crust and then move the delivery to other areas to similarly provide holes in the crust which will ultimately join together to form small crust islands. At times during the operation, it is also necessary to discharge the manure slurry tangentially around the tank to provide a swirling action and break the crust loose from the wall of the tank.
With the system described in U.S. Pat. No. 4,332,484, the over-the-top nozzle could be adjusted in a horizontal plane by loosening the coupling of the pump outlet to the vertical delivery pipe and then rotating the delivery pipe and discharge nozzle. Loosening the coupling during operation of the system often resulted in substantial leakage until the coupling was retightened, and as the adjustment was carried out at ground level, the operator could not accurately determine the position of penetration of the liquid slurry into the crust.